Method for treating ferruginous waters.



L. S. HUGHES & C. H, WOLCDTT.

METHOD FOR TREATING FERRUGINOUS WATERS.

APPLICATION FILED SEPT. a 1914.

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LOUIS S, HUG-HES AND CLIFFORD H, WOLCOIT, 0F GHICAGO, ILLINOIS.

METHOD FOR TREATING.FEBRUGINOUS WATERS.

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To all whom it may concern:

Be: it known that we, LOUIS United States, and residents ofChicago, in the county of Cook and State of Illinois,

have invented certain new and useful Im as mine'water, wherein free sulfuric acid is.

present as Well as metallic salts, such as sulfates of iron and aluminum, and, generally stated, the invention contemplates a method by which the acid constituent may be neutralized, wherebyto render the water availtemplation the'provision of a method susceptible of treating strong acid water so as able for use for industrial purposesand also by which by-products may be recoveredin merchantable form valuable for use in the mechanic arts. j

More specifically set forth, the invention has todo with a method or process of the general character before referred to made the subject of a co-pending. a plication for Letters Patent of the United tates, filed by Louis S. Hughesunder date of October 2,

1913, and bearing Serial No. 792,960. In

that application is disclosed a method of treatment which embraces the utilization of p a raw carbonateof an alkali earth, such as limestone, arranged in separated bodies to provide successive stages 1 of'treatment, the limestone of each body being ingranular form and graduated in size so that the particles of each body will be relatively larger than the particles of" the preceding body, and through these limestone bodies the acid ulous Water is progressively passed. During such passage the carbonate reacts on the acid constituents of the water to neutralize these acid constituents and form a precipitate in suspension, which precipitate, after leaving the limestone, .is subjected to violent agitation in order vto coagulate the same and thus enable the precipitate to settle in a proper it and therefrom to be removed for such rther treatment as maybe necessary to render it commerciallymseful. We havefound, however, that while the method or .process in, question is eficacious for neutralization of the acid content in the weaker acidulous waters and for the removal of ferricsalts, the treatment afforded does not precipitate the ferrous salts, so that all the iron held by the water is not recovered Specification of Letters Patent.

S. HUGHES and CLIFFORDH. WOLCOTT, citizens of the Patented Jano 15, 918.

Application filed September 8, 1914. Serial No. 860,569.

Furthermore, when strong acid water is treated'by the method aforesaid it is diflicult to obtain complete neutralization by the use only of limestone, an excess of calcium sulfate being produced which is partially precipitated with the iron salts and forms an undesirable ingredient forpigment production. p

The main and primary object of the pres ent invention, therefore, is the provision of a novel method for the treatment of acid water whereby the ferrous salts may be readily converted into ferric salts, and thus be rendered precipitable in order that the precipitate -.shall include all of the iron carried by the water.

7 Further, the invention also has in conto obtain complete neutralization thereof,

precipitate, therefore, is highly useful for pigment production and is wholly free from objectionable ingredients.

A further object of the present invention is to eliminate the gradual incrustation of the carbonate employed as a precipitant, the limestone used under the conditions obtainingin the practice of the method of the previous application referred to being open to this objection. r p

Other ob'ects'and advantages of the invention will be apparent as the nature of the improvements is better understood, the invention consisting in thenovelsteps hereinafter fully described and recited in the appended claims, and while the adaptation of the invention as specified is believed at this time to be a preferred embodimentthereof,it is obvious that it is susceptible to various changes or modifications without departing from the spirit of the invention or sacrificing any of its advantages.

In the drawings: Figure 1 is a diagrammatic view illusthe herein-described invention.

Fig. 2 is a detail sectional lplan view of the settling pit and the coagu dischargin thereinto.

As speci fore referred to, the water to be treated is primarily that discharged orpum ed from coal mines, and contains as Well as metal ic sulfates, but it is'mani trating a form of apparatus for practising v t ating trough? ed in the application hereinbe-' i free sul ric acid fest that the methodv may be employed with other waters which. it is desired to treat and from which! it is also sought to extract the metallic content. No s ecial apparatus is necessary for carrying into effect the pres-- ent invention, but the accompanying drawings illustrate a schematic arrangement adapted for the purpose. In contradistinction to flowing the acidulous water over or through limestone bodies having a fixed status, such as disclosed in the aforesaid application, it is the purpose ofthe present invention to subject the water in its flow to the action of a body of limestone in granular form contained within a pulverizing de vice, such as a tubular ball mill. This is conventionally illustrated in the drawings and designated by the numeral 10, and is of suflicient size to contain the requisite quantity of the limestone for the proper treatment of the water as the latter passes through the mill. tains the necessary ball members so that, by the attrition of the latter against the limestone particles, a grinding action may be effected to produce a very fine limestone powder. Thi is taken up by the water, which is introduced by a, trough 11 from the source of discharge of the water, .and as the latter passes through the mill 10 it will be apparent that the powdered limestone will react to neutralize the acid contained in the water. A precipitate -.in suspension results. The water with the precipitate then passes into a collectin vat 12 wherein the flow of the water is partially retarded, and at which point the reaction may be observed, and from'the collecting vat 12 the water and the suspended precipitate pass down an inclined trough 13 in which is arranged a series of transversely-extending bafilesdesigned to impart vio'lent agitation to the water and to theprecipitate as the same pass from the vat 12. This agitation of the water serves to coagulate the suspended precipitate' and prepares the same for settling when the Water and the precipitate reach a conical pit 14 into which the coagulating trough 13 discharges. The discharge of "the trough 13 into the pit 14 is tangential to the latter so that the water is given a whirling action in the pit and thus the precipitate is caused to settle at the bottom of the pit 14 from which it may be removed by a pipe 15 connected to a suitable pump line.

As before stated, the action of the limestone as a precipitant serves to precipitate the ferric salts contained in the water, but the ferrous salts are not susceptible to this action by the limestone. To convert the ferrous salts intoprecipitable'form is one of the objects of thisinvention, and to the accomplishment of this end it is proposed to introduce into the acidulous water an It, of course, also con-' oxidizing reagent through, the medium of which the conversion referred to is effected.

'For this purpose the oxidizing reagent is it is preferred to'employ a soluble hypochlorite such as calcium hypochlorite or bleaching powder. The effect of this, as is obvious, is to react on the ferrous salts to convert the same into ferric salts, and thus when the water enters the ball mill 10 and is subjected to the action of the carbonate therein, the converted salts are susceptible to precipitation by the carbonate. The by pochlorite being of a basic character also neutralizes its equivalent of the acid content of' the water. 1

As also stated, the present invention contemplates the production of a precipitate which is free from calcium'sulfate or gypsum. When treating water which is'strong in acid it is commercially undesirable to complete neutralization by limestonealone, clue to the fact that such a quantity of calcium sulfate is produced that it partially precipitates with the iron'salts and forms an undesirable ingredient forpigment production. In such cases a precipitate free from gypsum may be obtained by limiting the treatment with lime compounds to such a point that the gypsum produced does not exceed the amount which will remain in solution and by completing the neutralization with calcined magnesite. To this end it is proposed to introduce the magnesite at'the point where the gypsum begins to manifest it self in the precipitate and before deposit of the precipitate in the settling pit, and in order that this may be done the magnesite may be introduced, as by a feed device 17, to the water in the collecting vat 12, which vat, by reason of its location in proximity to the mill 1O and'between the latter and the coagulating trough 13, will retard the flow 01' the water and the suspended precipitate for a sufiicient period to permit observation and inspection of the precipitate from time to time: When themagnesite is so introduced neutralization is completed and the. precipitate contains no gypsum. The produced magnesium sulfate does not precipitate be= cause of its high solubility.

From the foregoing the operation of,the herein-described process will be readily seen, and, briefly stated, is as follows: The acid water as it flows or is pumped from the mine passes through the trough 11 and is.dis-' charged thereby into the mill 10. This being in operation, thecrushing balls act upon the limestone particles to gradually reduce the same to a powder which, acting upon the acid water, will neutralize the acids in the water and produce a precipitate in suspension. This precipitate is colloidal in form and as the precipitate is discharged into the collecting vat 12 the flow of the water is retarded for a brief period to permit the further spontaneous formation of the precipitate in the water. At the same time this relarding of the flow enables determination of the character of the precipitate and if it be found that gypsum is manifesting itself the proper steps may be taken to limit the action of the limestone and to feed into the water a proper amount of magnesite for the purpose of eliminating the gypsum. From the collecting vat 12 the water passes through the inclined coagulating trough 13, in which passage the Water and the precipitate are subjected to agitation so that the minute particles of the precipitate are massed together to thereby coagulate the precipitate, whereupon the water and the precipitate are discharged into the settling pit 14, which discharge is attended by a whirling action of the water in the pit for settling of the precipitate therein. The precipitate may be pumped from the pit 14 through the pipe 15 and the water, freed of the precipitate, may then pass out of the pit 14 in its purified state.

As before set forth, the ferric salts will be precipitated by the limestone, but to convert the ferrous salts into ferric salts in order to accomplish precipitation of the former, an oxidizing reagent is discharged into the trough 11 from the feed device 16 so that the acid water may be introduced into the mill 10 charged with this oxidizing reagent.

The herein-described process is primarily designed for the production of a pigment and in the formation of the latter it is highly desirable that the same shall be free of calcium sulfate. 1 This result is obtained by the magne'site. By controlling the operation of the ball mill the quantity of pulverized stone gradually produced therein may be limited to the amount required to neutralize the acid constituents of the water so that the precipii tate is substantially free from limestone. It more limestone be pulverized than is 1'8!- quired for neutralization, the excess thereof will be collected with the precipitate and contaminate the same. This is undesirable and the production of pulverized limestone may be nicely regulated to the desired amount by'controlling the operation ofthe ball mill, as above indicated.

Having thus described the invention, What is claimed as new and desire to be secured by Letters Patent is:

1. The method of treating ferruginous water, which consists in subjecting the water to the action of an oxidizing reagent to convert the ferrous salts into ferric salts to re d r the to al iron content of the wa er &

water the step which consists in subjecting the water to the action of a soluble hypochlorite to convert the ferrous salts into ferric salts to render the total iron content of the water precipitable.

3. The method of treating ferruginous water, which consists in initiating neutralization of the acid' content of the water by the action of a reagent capable also of rendering insoluble the precipitable metallic content and which forms a substantially insoluble salt with said acid content, and then completing neutralization and precipitation by subjecting the water'to the action of a second reagentforming a readily soluble salt with said acid content.

4:. The method of treating ferruginous water, which consists in initiating neutralization of the acid content of the water by the action of a reagent capable also of rendering insoluble the precipitable metallic content and which forms a substantially insoluble salt with said acid content, then completing neutralization and precipitation by'subjecting the water to the action of a second reagent, and then recovering the precipitate.

5. The method of treating ferruginous water, which consists in initiating neutralization of the free acid of the water by the action of a reagent capable also of rendering insoluble the precipitable metallic content, and which forms a substantially insoluble salt with said acid, and then subjecting the water to the action of magnesite, whereby to complete neutralization.

6. The method of treating acid water, which consists in initiating neutralization of the acid content in the water by the action of a reagent capable also of precipitating the iron and aluminum in the water and which forms a substantially insoluble salt with said acid content, then completing the neutralization and precipitation by sub jecting the water to the action of a second reagent forming a soluble salt with said acid content, and then recovering the precipitate.

7. The 'method of treating ferruginous water containing free sulfuric acid, which consists in initiating neutralization of the free acid by the action of limestone, whereby the iron content is precipitated ,and a relatively small amount of sulfate of calcium is formed, andthen completing the precipitation and neutralization by subjecting the water to the action of an alkaline carbonate which forms a soluble sulfate with said acid and completes the precipitation of the iron.

8. The method of treating ferruginous water containing free sulfuric acid, which consists in initiating the neutralization of the free acid and the precipitation of the iron content by treatin the water with limestone, and then compfiating the neutralization and precipitation by treating the water with magnesite.

9. The method of treating ferruginous Water, which consists in subjecting the Water to the action of an oxidizing agent to convert the ferrous salts into ferric salts, then subjecting the water to the action of limestone to partially neutralize the Water and precipitate the iron as a ferric salt, and then completing the neutralization and precipi-tation by subjecting the water to the action of magnesite.

LOUIS S. HUGHES. CLIFFORD H. WOLCOTT.

Witnesses:

CHARLES G. SPOERER, WniuAM F. SEIDLER. 

